NEW YORK, NY (September 5, 2012)—Twitter is continuing to grow at a rapid pace, eMarketer estimates, with 106.7% growth predicted for this year as the company reaches $288.3 billion in global ad revenues.

Out of all of the social networks included in eMarketer’s September US ad spending forecast, Twitter will experience the steepest growth. eMarketer has raised its expected growth rate significantly for 2012 from 75% to 94% in the US alone. Between 2012 and 2014, Twitter’s US ad revenue will climb from $259 million to $638 million.

The social network’s rollout of a self-serve advertising platform, rapid international expansion and Twitter’s success at signing big-name advertisers to longer-term ad packages have led to faster-than-expected growth. It is also expected that in late 2012 or early 2013, the social network will release an Ads API as well as begin distributing TV and video content, opening up more revenue streams. Mobile revenue will also be a main driver of Twitter’s growth. Mobile clickthroughs will be higher because many users are more active on the site via mobile devices than desktops.

Throughout eMarketer’s forecast period the microblogging service is expected to maintain worldwide growth in the high double digits, reaching $807.5 million in ad revenues by 2014.

Much of the company’s growth is driven by its mobile presence. Twitter will earn $129.7 million in mobile advertising revenues this year in the US, eMarketer projects. By 2014, Twitter is expected to earn more than $444 million in US mobile ad revenues alone.

eMarketer estimates that 55% of Twitter’s ad revenue will come from online advertising, this year while the other 45% will come from mobile. This large share illustrates the strength of mobile advertising for Twitter. By 2014, Twitter’s mobile revenue share will surpass the company’s online revenue, at 55%, eMarketer estimates.

As users increasingly access Twitter via mobile devices, eMarketer believes that the tight integration between the company’s ad products—particularly Promoted Tweets—and core user experience has made the subsequent shift toward displaying mobile advertisements relatively simple. Twitter CEO Dick Costolo has reported that, on most days, the service generates more ad revenues from users on mobile devices than it does from viewers of Twitter.com.

eMarketer bases its estimates for Twitter advertising revenues on an analysis of company reports; estimates from other research firms on advertising revenues, pricing, impressions and other factors; usage trends at major mobile advertising publishers; and eMarketer interviews with executives at ad agencies, brands, online ad publishers and other industry leaders.

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